1. Field
The following description relates to technology to expand a dynamic range of a camera.
2. Description of the Related Art
The dynamic range of a camera is a ratio between the maximum and minimum measurable light intensities. As the dynamic range widens, the quality of representation of an image increases. Currently, commonly used digital cameras have a dynamic range of about 50 to 60 dB, which is significantly smaller than the dynamic range of human eyes, which range from about 100 to 120 dB. The dynamic range of sensors used in digital photography is many times less than that of the human eye and generally not as wide as that of chemical photographic media. In digital imaging, algorithms have been developed to map the image differently in shadow and in highlight in order to better distribute the lighting range across the image.
As one example of a method for overcoming such a limitation of the dynamic range of a digital camera, two images with captured with different exposure times can be blended together to form a composite image. The images obtained with different exposure times have different dynamic ranges, such that the composite image can have an improved dynamic range.
However, if an object is photographed continuously over a predetermined time interval, image inconsistency (for example, a ghost image and motion artifacts) may occur due to movement of a camera or the object. In light of this, there is a method to prevent image inconsistency: a region of each image, in which motion occurs, is detected and adjusted, and, if the detected motion is large, one of images is selected without compositing images.
The method of adjusting the region in which motion occurs increases the amount of operations performed for detecting and adjusting the motion. However, this method used to prevent image inconsistency by selecting one image has the disadvantage of not having an effect of expanding a dynamic range, and thus this method is not appropriate to expand the dynamic range in a dynamic environment.